The present invention relates to a method and an apparatus for splitting samples of particulate matter, which may be applied both to dry powders and to particles which are suspended in liquids.
Methods and apparatus for splitting samples are used both in production and in laboratories when representative samples have to be prepared for assessing the quality of large product quantities of particulate matter. The manual methods of sample splitting include collecting samples of large product quantities (trucks, shiploads, railway wagons) and splitting them into analysis samples by coning and quartering, which is used for feed material quantities of up to approximately 1 m.sup.3.
Static sample splitters are used when smaller feed material quantities of up to approximately 0.1 m.sup.3 are to be reduced into analysis samples. However, for the purposes of measurement in a laboratory, final sample amounts or quantities of only a few grams (e.g. for screen analysis) down to a few milligrams (for sedimentation analysis) and even less than 1 mg (for counting methods) are generally required. Therefore, in the case of both large and medium-sized initial or sampling quantities, the efforts involved in sample splitting increase and the quality of the sample splitting must become more reliable as the reduction to smaller analysis samples via subsamples increases. For reasons of statistical certainty when obtaining and ensuring the representative composition of the reduced subsamples, each of these subsamples must be composed of as many even smaller subsamples as possible during the splitting of the samples. The manual effort involved and other reasons restrict the reliable applicability of static chute splitters for the purpose.
Spinning chute splitters bring about much more reliable sample splitting results because only very small final systematic errors must be expected as the initial amount of material is subdivided into thousands of subsamples (14,400 subsamples of approximately 35 mg may be obtained by a riffler splitter which divides the incoming stream of particles into eight subsamples, when in 15 minutes 500 g are fed to the riffler spinning at 120 rpm). Extremely small representative analysis samples can be taken only from pastes or suspensions because only then a subsample may be taken as a random sample from the homogenously mixed material. Pastes are indispensable when large particles would be deposited as sediment in suspensions.
Therefore, it is an object of the invention to provide a novel and useful method and apparatus for sample splitting to obtain extremely small analysis samples from large amounts of feed material with extremely low systematic or statistical errors without having to apply sample splitting in pastes when the sample contains coarse particles.